What happens if no car manufacturer can pass the test?
Does this mean the law is unrealistic or the car manufacturers wrong?
And why exactly do we need diesel cars?
It means that diesel vehicles are very polluting and unless there is good rationale for individuals to own such vehicles, they should not be allowed.
I imagine that if the cheating car companies (VW) cannot provide an economical “fix” that provides decent performance, those who bought diesel cars under false promises will be grandfathered into new regulations, but that is a limited solution. Personally I think diesel for passenger cars is dead. No resale value.
Historically, diesel has been seen as stinky and polluting. I’m angry at VW (a company whose products I have bought and liked) for pushing the idea that it could be anything but. We’re in the market for a new car. I was seriously considering buying a diesel Passat based on the rah-rah publicity surrounding “clean diesel…” I’m glad I did not. although I can’t claim any superior insight, just luck. I’ll probably buy a Honda Accord now (Acura if I can afford).
You can but it’s more expensive.
Adding a urea injection system can probably bring the vehicles into compliance just like lots of other diesels. It’s what they wanted to avoid in the first place.
That appears to be more of a problem with the European tests being unrealistic as far as simulating real world driving goes. It may not be just diesel cars that have worse emissions (and fuel consumption) in the real world compared to European tests.
Diesel cars are indeed more polluting, due to the lower refinement of the petrol. However, they have wonderfully peppy engines, which is exactly what is impacted when they do a good job with emissions control.
Actually, the high NOx emissions are due to the lean burning characteristic of diesels (that is also a problem with lean burn gasoline engines). Diesel fuel is now required to have much lower sulfur content than before 2007, allowing better emission control than before, though NOx is still the difficult part of the emission control equation with diesel engines (as opposed to CO and HC for most gasoline engines).
I don’t know but diesel cars have fume that smell terrible, whenever we are close to one, I have to roll my window up so it can’t be good for the environment.
And let’s not forget that some major public transit agencies have been bragging about their “clean diesel” bus fleets for years. Do those buses actually emit less pollutants? That’s what we thought about Volkswagen.
Diesel fuel is slow burning compared to gasoline, it has decent torque but is going to give in general a lot slower performance than gasoline (yes, there are very fast turbo or supercharged diesel engines, that are quick, but they also put out pollution that means they likely are not street legal). Diesels have other issues, they have trouble with particulate emissions because diesel fuel is less refined, and they also can be hard to control because of the nature of the combustion, because it basically uses superheated air from high compression to ignite the fuel).
I also have heard the myth diesel cars are more efficient than gasoline powered cars, and that isn’t true. Diesels do better fuel mileage primarily because diesel has a lot more energy content (measured in BTU’s/gallon), if I remember from thermo diesels and gasoline engines are roughly the same efficiency. Diesel rigs moving 40 tons do 6 mpg, but they do it because diesel fuel is lower on the distillation process so will have more BTU content.
I personally think you would be a lot better off with a high efficiency gasoline engine than a diesel, for a lot of reasons. While modern diesels are a lot better than the clunkers, like the GM diesel that was converted from a 350 small block gas engine, diesel IMO is still much better used in large scale transportation, like trucks and ships and train engines, whatever benefits you get out of it to me is outweighed by the negatives of it. I wouldn’t be surprised if they figured out in real world tests that all diesels pollute a lot more than the EPA cert testing showed, diesel has very different characteristics than gasoline engines and my (limited) experience with them is they just don’t clean up as well as gas engines have.
Actually, it has been true until the relatively recent levels of emission standards – diesel vehicles’ fuel efficiency exceeded that of gasoline vehicles by much more than the higher energy density of diesel fuel versus gasoline (about 8% higher for diesel fuel). The more recent levels of emissions standards now make containing NOx emissions very difficult to do for diesel engines without cutting back on fuel efficiency, so the fuel efficiency advantage of diesel engines now is much less than it was about 15 years ago. From http://www.fueleconomy.gov :
2015 EPA combined ratings for VW Golf:
36 diesel, 30 gasoline – diesel 20% better, but with cheating (although the EPA fuel economy does come from the same test as for emissions, so any cost to fuel economy from running in “low emissions mode” for the test should be reflected in the EPA fuel economy – though running in “low emissions mode” all the time on the road may have unacceptable costs in power, drivability, reliability of emissions components, etc., which is presumably why they cheated)
2000 EPA combined ratings for VW Golf:
38 diesel, 24 gasoline – diesel 58% better
Basically, improved engine technology has allowed gasoline engines to catch up with diesel engines in efficiency while still meeting tightened emissions limits, while improved engine technology in diesel engines has all gone into reducing emissions, and it may still not be enough to meet today’s emissions limits without either cheating or completely giving up the fuel efficiency advantage. This was even with the drastic reductions in the sulfur content of diesel fuel.
@ucb:
You are correct, I had to go back and look up the numbers and the reasons why, and it should have dawned on me why. The Diesels operate at a very high compression ratio (around 22-1) which also means higher heat which in turns means more fuel burns (the efficiency of a heat engine is roughly t2-t1/t2, where t1 is the ‘cool’ temperature in the cycle of the heat engine). If you increase the compression ratio of a gas engine, you get pre-ignition, so they are limited to roughly 10.5-1 as a max (some went higher, but you had to run very high octane gas to prevent knocking; these days engines retard the timing automatically if they detect knock), whereas with a diesel pre ignition is ignition…
I suspect you are correct,that to meet emissions regs they won’t be as efficient (in effect, they are probably messing around with at what point the diesel fuel is injected, and if you inject it not at top dead center, you lose performance but pollution will be less I would guess; not an expert on diesel engines at all). Gas engines have a lot more latitude in controlling combustion because they use spark ignition (it is interesting that diesel fuel is desired to have a lowered cetane rating (basically the analogy of octane in gasoline), because they of course want it to ignite easily.
I never particularly liked diesel engines in cars, in boats and trucks they make a lot of sense (put it this way, a marine diesel is a lot safer than a gas engine in a pleasure boat, talking an inboard), but in a car the extra weight and other tradeoffs made no sense, in europe they are popular because of the cost of fuel and also in many countries the taxes on diesel powered cars (the equivalent of our registration fees) are less than a comparable gas engine car. I also believe that diesels, even though cleaner than they used to be,still get breaks on things like particulate and sulfur emissions, and I really wonder, even without cheating, how clean diesels run down the road so to speak, if they stay so clean.
Personally, I am waiting to see what happens with a couple of recent things I have been reading. Apparently in australia they have developed an ‘artificial leaf’ that can produce hydrogen quite cheaply, and several of the Japanese car companies are planning to push fuel cell technology, with the two of those, it could be the breakthrough we have been looking for, in that hydrogen distribution could be done pretty much the same way we do natural gas, so you could have filling stations and such that act as both gasoline and hydrogen filling stations (and if one more idiot talks about the Hindenburg, I’ll scream, hydrogen is less explosive than gasoline vapor).
Recreational motorboats (whether gasoline or diesel) have much worse emissions than on-road vehicles.
In Europe, fuel prices were and are much higher than in the US for both gasoline and diesel. Diesel fuel may have been slightly lower priced, but the huge (about 15 years ago) fuel economy improvement for the diesel option made them more popular. Now that the difference in fuel economy has narrowed, the attractiveness of the diesel option is much lower today.
Current US emissions limits are the same for gasoline and diesel vehicles. Note that the testers in the US that found the discrepencies in the VW diesel were also driving a BMW diesel that stayed within the emissions limits. The discrepencies found in Europe may be more related to the design of European tests that can result in unrealistic emissions and fuel consumption performance, even if there is not a different engine computer program for the test versus otherwise (this can affect gasoline engines as well).
Yep, since 2007 they are supposed to meet the same standards, tells you how far I have been out of gearhead space read an article that said the only way to really test cars is to do measurements on highways and such, that it would be possible to monitor cars in the real world and see if what their OBDII units report during testing in fact is the truth. In a less scientific mode, having been behind modern diesels in an open car, while they are nowhere near as foul as they were 40 years ago, they still seemed to me to be putting out more crap (or maybe it was simply smelled worse).
In terms of marine motors, I was thinking more safety than emissions, inboard gas marine engines because of gasoline vapor cause a lot of fires and explosions, something you don’t have with diesel fuel (most of it is the stupidity of the owner, forgetting to have the vent fan running before starting the motor).
I just don’t think that Diesels are the solution to fuel mileage and I think even with all the technology that have been applied that they aren’t the answers for cars and I think trying to get more people to use diesels makes no sense in the US, it is a step backward, not forward. It is interesting that even though gas prices have dropped to really low levels, diesel fuel is still more expensive. When I was growing up diesel was the price of regular gas or lower, these days it is significantly more expensive. From what I have been told, the reason is that in large part because of demand for diesel fuel remaining high because they are common in Europe, and its use in long haul trucking, it always has more demand than gasoline and hence the price differential.
I personally do not notice any smell around any car from the last few years (gasoline or diesel; even the “cheater” VWs do not smell). Now, old trucks which seem to stay in service a lot longer than cars are a different story… somehow, they make a lot of smelly soot even on ultra low sulfur diesel fuel now required for road use. Old gasoline cars are rather smelly also, although there are fewer of them around.
For a motorboat engine, seems like you would want a well sealed fuel system to avoid having fuel fumes all over the place, from a safety, comfort, and emissions standpoint, regardless of what fuels the engine. In terms of emissions, old motorboats compete with old trucks for nasty emissions.
As far as the price of diesel fuel versus gasoline, it is now lower for diesel fuel locally, after some years of being higher. The prices of diesel fuel and gasoline do not always move in tandem. Diesel fuel is similar to jet fuel and heating oil, so changes in demand for one can affect the prices of the others.
Diesel is still more expensive here, gas prices are very low in NJ in general, but diesel is higher. WIth gasoline engines in pleasure boats, the problem is when you fuel, gasoline gets into the bilge and puts out fumes and those become explosive vapor. On boats they are required to have blowers in the bilge to vent the fumes, but a lot of people aren’t too bright, they refuel, then forget to do that, and boom…
Diesel fuel and heating oil are pretty much the same thing (you can run heating oil in a diesel), so the yield from a barrel of oil is higher, jet fuel is basically Kerosene, and is more refined (the least yield per barrel is gasoline, since it is highly refined). There are price effects with supply depending on what they choose to produce. All are affected by the base price of oil, of course, but they also do interact with each other as well, if it is cold and they produce a lot more heating oil, they will produce less gasoline or jet fuel, and the prices of those may rise if demand otherwise is unchanged
One of the big differences is with gasoline there is a lot more of a change in behavior that can cause gasoline prices to drop because demand drops in response to price increases. Thus, when the price of gasoline goes up, people’s behavior changes, and they find ways to use less gas (they drive less, they use mass transit, buy more fuel efficient cars) and demand drops, so the price will drop. With Diesel, because it is used for more than personal driving , for things like trucking and trains where demand cannot easily drop and because of the heavy use of diesel cars in Europe, where driving already is a lot less than the US (thanks to high prices for fuel, access to trains, etc), demand doesn’t drop much, so the price doesn’t drop as much.
Seems like motorboat owners need to be careful about avoiding fuel spills and fixing leaky fuel systems. The vapors, even if they are blown out without catching fire, contribute to air pollution.
Heating oil in many states can still have a much higher sulfur content than on-road diesel fuel (15ppm since 2007). NY has required <15ppm since 2012, and MA, NJ, and VT required <500ppm in 2014. Some states will reduce the sulfur limit in heating oil in future years. See http://www.eia.gov/todayinenergy/detail.cfm?id=5890 .
Putting heating oil with higher sulfur content in a diesel engine will result in higher soot emissions and/or damage to the emission components. There are also penalties for tax evasion for using fuel on which road-use taxes have not been paid.
Jet fuel is close enough to diesel fuel that diesel engines can use it, although there may be issues with sulfur content, lubricity, and other properties of the fuel, as well as road-use taxes.